The present invention relates to a system comprising a storage device and a computer that are connected via a network.
A system in which at least one storage device is connected to a plurality of hosts via a network has come into wide use in recent years in place of a system in which the storage device is directly connected to the computer (also referred to hereinbelow as a “host”). The connection of storage devices using a network is called a storage area network (referred to hereinbelow as a “SAN”).
A SAN has heretofore been constructed by using fibre channel (referred to hereinbelow as “FC”) technology. A SAN constructed by using FC technology will be referred to hereinbelow as a FC-SAN. A host and a storage device connected to an FC-SAN operate to conduct data write/read operations to/from a storage device by sending and receiving a SCSI (Small Computer System Interface) command or data by means of FCP (Fiber Channel Protocol).
On the other hand, an IP-SAN, which is a SAN constructed by using an IP (Internet Protocol) network has recently attracted much attention. When a host and a storage device communicate via an IP-SAN, the iSCSI protocol, which is a protocol in which SCSI commands or data are capsulated with TCP/IP (Transmission Control Protocol/Internet Protocol), is mainly used.
Among devices conducting communication via the above-mentioned FC-SAN or IP-SAN, those devices that send commands requesting data write/read operation or write data (either physically or logically) are called initiators. On the other hand, devices that receive a write command or data from an initiator and write the data into a storage device, such as a hard disk drive, or that receive a read command from an initiator, read data from a storage device and send this data to the initiator (either physically or logically) are called targets. Further, an initiator and a target are together referred to as a node. Usually, a host serves as an initiator and a storage device serves as a target. However, when data replication is conducted between storage devices, a storage device that stores original data serves as an initiator, and the other storage device that stores a replica of the data serves as a target.
In a FCP, an initiator and a target are distinguished by a WWN (World Wide Name), which is an address assigned to a physical port of an HBA (Host Bus Adapter) or a physical port of a storage device. Here, an HBA is a device attached to the host for conducting communication processing using the FCP. A WWN is an address inherent to a physical port and cannot be changed by a system administrator or the like.
On the other hand, in the iSCSI protocol, an initiator and a target are logically distinguished with an identifier called an iSCSI name. An iSCSI name is a character row which does not exist in the physical port and can be changed by a system administrator or the like. Therefore, for example, an iSCSI name assigned to a certain storage device can be reassigned to another storage device.
A process of replacing a storage device connected to a SAN such as an aforementioned FC-SAN or IP-SAN with another storage device due to insufficient capacity or functionality is called a migration of storage devices. Migration also includes a change of a storage device storing data according to changes in the data read/write frequency or importance.
For example, a method is described in Japanese Patent Application No. 2003-108315 as a technology for rapidly conducting migration using an FC-SAN.